First, I would talk to both John and Sally together after class, and explain several things to them so they know where I stand. I would tell them first off that I understand that they are dating and that it's natural for them to want to sit together during class. I would, however, also tell them that they need to make sure they stay focused in class, which includes keeping a reasonable distance between each other, and acting in a manner that's appropriate. After this, I would continue to monitor them closely during class periods to make sure that they are acting in an appropriate manner. If I noticed any inappropriate behavior, I would let them know immediately that it needs to stop. If the problem continued, the I would make sure to call home. In all actions, it's important to remain aware and sensitive to the students' feelings while enforcing and encouraging appropriate behavior.
By Thomas White